Workpiece handling machines including rotating turrets, carousels or turntables for carrying workpieces to and from one or more work stations where various operations may be performed on the workpieces are well known. These machines are particularly useful when a large number of objects need similar treatment because they allow the positioning of a plurality of workpieces at a work station sequentially and repetitively without substantial manual labor.
U.S. Pat. No. 3,357,396 disclosed a turret-type indexing machine for coating the interior of a can. The machine includes an opposed pair of turret members and two pairs of nozzles. A motor driven chain and helical gear and cam assembly operates both the nozzles and turrets; the cams are designed to provide dwell periods whereby the turrets remain stationary while spraying operations are performed on the cans. Chain driven rotatable disk members contact the sides of the can to rotate them while spraying operations are being performed.
U.S. Pat. No. 2,719,387 discloses a blasting apparatus for abrading the internal surfaces of open-ended, hollow workpieces. A ratchet drive assembly, including a notched ratchet gear wheel, two latching pawls and an advancing pawl, drives and locks a circular table so that a workpiece, held by a work holder, may be treated by a stream of blastant material.
Other patents disclosing machines for sand blasting, cleaning or coating that include turntables or carousels for moving a workpiece from work station to work station include U.S. Pat. Nos. 4,753,051, 4,084,357, 3,240,216, 2,725,685 and 2,725,063. The machines disclosed in these patents representatively include intermittent direct drive (patent '216), cam/stop arrangements (patent '685), or electromagnetic mechanisms (patent '063) for indexing and locking workpieces between or at work stations.
One of the problems with rotatable turntable or carousel type indexing machines is that once the turntable and workpiece supported thereby is properly positioned, there has to be a method or means provided to lock the turntable into position so that work may be carried out. As evidenced by the above prior art, a plurality of pawls (patent '386) or cams that provide dwell periods (patent '397) have been used to accomplish this locking.
Another problem with the rotating turntable type machine is that controlling the various machine operations typically requires a trained operator or a plurality of mechanical or electro-mechanical control devices. A trained operator obviously generates significant expenses and the mechanical or electro-mechanical type control devices require substantial maintenance because of normal wear and the generally hostile environment of use.
A substantially computer-controlled, indexing-type cleaning machine adapted for moving a plurality of combustion chambers to and from a work station without requiring multiple, complicated locking or mechanical control features would be a decided improvement over the indexing or turret-type machines disclosed in the prior art.